Adding memory to a system is one of the most useful upgrades you can perform, and also one of the least expensive. Upgrading memory can boost your computer's performance by 50%.
Too many of the manufactured computers come with barely enough to run the system adequately. Each operating system comes with specifications for minimum and recommended amounts of memory.
Although the computer may function with 4GB of RAM or even less, generally 8GB is a reasonable minimum when using the newest versions of Operating Systems. Especially computers running under Windows 7 should have at least this much.

Not all computer memory is the same. Most computers in use today use DDR3 types of memory for their main system memory. It's not only important to purchase RAM that's compatible with your computer, it's important to choose top quality RAM. A small dose can give your computer's performance a big boost.

Memory is so important that it cannot be wasted. RAM is allocated by the operating system and programs, and then released when not needed. Errant applications can grip RAM and not release it, which results in a diminishing amount of memory available as you load and use more programs.